Normal baking issue, some parts are low res
This is a good video about baking good normal maps in Blender. Some similar issue resolving happening here: https://youtu.be/0r-cGjVKvGw?t=8m26s

Don't know if this helps for your problem, though. Edit, whoops, only now I noticed you used xNormal for baking instead of Blender. Oh well...

To sum it up, the issue in the video was this:



And the solution was to put value 0.05 instead of 0.1 to the 'Ray Distance' field and bake again.